Brazing mechanism of Al0.1CoCrFeNi with composite structure nano-multilayer foils: Molecular dynamics and experimental perspectives

A defect-free brazed joint with an FCC + BCC dual-phase solid-solution structure was successfully fabricated using an Al_0.1CoCrFeNi high-entropy alloy (HEA) with novel nano-multilayer foils. This study combined molecular dynamics (MD) simulations and experimental methods to elucidate the interfacial diffusion behavior and microstructure formation mechanism during brazing. MD simulations revealed that joint formation progressed from the initial nano-multilayer structure to a disordered solid solution, followed by wetting from a molten Al phase, and culminating in a solid-solution reaction. Experimentally, the joint microstructure was found to consist primarily of a hard BCC (Al-Ni-rich) phase and ductile FCC (Co-Cr-Fe-rich) phase. The formation of this homogeneous solid-solution zone was attributed to extensive atomic interdiffusion and intense interfacial reactions promoted by the high-entropy effect. The brazed joints exhibited maximum shear strengths of 308.5 MPa at room temperature and 292.8 MPa at 1073 K. This study demonstrated that nano-multilayer foils can effectively serve as HEA filler materials, thereby expanding the potential applications of HEAs and providing a novel and reliable strategy for joining Al_0.1CoCrFeNi HEAs.